1. Field of the Invention
This invention relates to a sound-attenuating communication headset useful in voice communications in a variety of settings.
2. Discussion of the Prior Art
Typical prior art sound-attenuating communications headsets incorporate an assemblage of components, generally including: at least one ear cup assembly including a speaker, a headband, a communications cable with a plug connector for connection to a source of electronic audio signals, a microphone boom assembly and, if there are two ear cups, an ear cup to ear cup connecting cable. Amplifier circuitry may be incorporated to provide electronic boosting of the electronic audio signal generated by the microphone. In addition, an inline push-to-talk (PTT) switch is sometimes incorporated in the communications cable. Typically, the various components are permanently fixed to other components of the headset or attached in a manner that requires the use of tools to separate them. Thus, for example, the microphone boom is typically mechanically clamped or glued to the ear cup in a permanent or not easily removable manner. Similarly, the communication cable is typically fixed in a more or less permanent manner to one of the ear cups. Within the ear cup, the speaker, as well as the circuit components, such as a printed circuit board, are generally connected by soldered junctions. Generally the repair or replacement of parts in such units must be done at a workbench rather than in the field. The microphones as well as the speakers, used in communications headsets, are generally susceptible to deterioration when exposed top water or water vapor, such as during use in adverse weather conditions. Typically, microphones and speakers are covered by a fine metallic screen or a plate with a series of small holes for the transmission of sound. The small openings in such covers may inhibit the passage of liquid water (not water vapor). However, water may form a film over the small openings and interfere with the transmission of sound.
U.S. Pat. No. 3,562,451 discloses a microphone and headset for use in aqueous environments and constructed with waterproof connections.
U.S. Pat. No. 4,875,233 discloses a communication headset having an earpiece assembly mounted on one end of a headband and a microphone retained thereon by an adjustably moveable boom.
U.S. Pat. No. 4,993,065 discloses an accessory communication device for telephone sets wherein a harness, to be worn around the user""s neck, has a microphone unit and a pair of earphones detachably fixed thereto.
U.S. Pat. No. 5,369,857 discloses a method of making a telephone headset wherein the headband and the microphone boom are formed by extruding a thermoplastic while simultaneously feeding two wires through the extrusion die. The resultant extrusion comprises two parallel lengths of solid conductive wire embedded in a thermoplastic extrusion. The wires serve to stiffen the extrusion and serve as electrical conductors.
U.S. Pat. No. 5,450,496 discloses a communications headset having a detachable receiver capsule rotatably and pivotally attached to a main body, and a cable pivot for allowing the headset connection cable to pivot with respect to the receiver capsule.
There remains a need for an improved sound attenuating communications headset suitable for use under varying environmental conditions and conveniently repairable or reconfigurable under field conditions.
It is an object of the present invention to provide a new and improved communications headset of modular construction that permits convenient repair or reconfiguration under field conditions by simple replacement of modules or components with similar or alternate modules or components, as necessary, without the need for tools.
It is a further object to provide a communications headset that is sufficiently water resistant to permit use in adverse weather conditions.
It is a still further object to provide a communications headset suitable for sharing in use between more than one user that can be hygienically cleansed by a simple procedure.
The above and other objects are achieved in accordance with the present invention, which provides a weather resistant sound attenuating communications headset comprising an assemblage of replaceable modules including:
a) a primary ear cup receiver module comprising an ear cushion, an ear cup membrane, an ear cup cushion plate, an ear cup foam sound barrier, an ear cup speaker, a printed circuit board assembly, and an ear cup shell;
b) a termination cable module adapted at one end for removable connection to said ear cup assembly and at another end for removable connection to a unit for the transmission and reception of electrical communication signals;
c) a headband module adapted for removable attachment on one end thereof to said first ear cup assembly module for securing and positioning said ear cup assembly module to engage a user""s ear;
the ear cup membrane being replaceably attached over the foam cover, speaker, and printed circuit board assembly to provide an hygienic and protective cover therefor.
The communications headset of this invention may be constructed as a monaural headset, that is, having a single ear cup receiver assembly module, or, preferably as a binaural headset wherein a second ear cup receiver assembly module is removably attached to a second end of the headband module to provide audio reception for each ear of the user. In the binaural headset embodiment, an additional modulexe2x80x94a headband cable modulexe2x80x94is included for the transmission of electronic signals from the termination cable module attached to the primary ear cup receiver module to the second ear cup receiver module. The headband cable module may be removably attached to the headband module and conformable thereto. For the transmission of electronic signals, the headband cable module may have a connector, such as a coaxial connector, on each end, for removable connection, in a known manner, to each ear cup receiver module.
The present communications headset is well suited for a variety of uses, particularly for uses in outdoor settings where adverse weather conditions and rough treatment are encountered. For example, in use by an airport ground crew, the termination cable may be plugged into a receptacle near the front of an airplane to provide a communications link to the cockpit. In a hurried disconnect, the end of the terminations cable is sometimes dropped and dragged on the ground and damaged as a result. Because of the modular construction of the present headset, the cable may be quickly and easily replaced in the field without the need for tools.
For use in two way communication, the communications headset of this invention may include a microphone, preferably a noise canceling microphone, held in a microphone boom module adapted for positioning the microphone at a suitable position with respect to a user""s mouth. The microphone boom module includes a flexible boom adapted at one end for removable connection to the primary ear cup receiver module. The connection provides a mechanical attachment to the ear cup as well as an electrical connection to the speaker within the ear cup. The microphone is held within a microphone housing at the other end of the boom. The microphone housing is covered with a microphone cover assembly comprising a protective membrane sealed within the microphone cover. The microphone cover assembly is removably attached to the microphone housing, for example by a xe2x80x9csnap fitxe2x80x9d onto the microphone housing. The flexible metal boom is preferably covered with a protective sleeve to provide additional water resistance. The protective sleeve is preferably a thin plastic or elastomer, such as heat shrinkable plastic cover or elastomeric tubing or sleeve.
The protective membrane sealed within the microphone cover is waterproof and serves to protect the microphone from the environment. The microphone cover assembly, including the membrane can be easily removed and replaced with no tools required. This offers a specific hygienic advantage in that the cover assembly, that is, the part that is near or in touch with the user""s mouth during use, can be easily replaced in the field when the headset is transferred to a new user. Similarly, the ear cup membrane serves to protect the components in the inner part of the ear cup receiver module, especially the speaker and printed circuit board, if present, from the environment. It also provides an hygienic advantage in that the membrane and the ear cup cushion, the parts that may be in touch with the user""s ear during use, can be easily replaced in the field, without tools, when the headset is transferred to a new user.
The water resistant thin film membrane material employed as a protective cover for the microphone as well as the speaker and amplification electronics in the ear cup receiver module(s) is a particularly advantageous aspect of the present invention. In each instance, that is, in the ear cup and in the microphone cover assembly, the membrane may be of the same or similar material, such as a flexible elastomeric film or sheet, but may vary somewhat in properties as well shape. The membranes may be fabricated from a variety of flexible polymeric thin film sheet materials, the preferred being a flexible thermoplastic polyurethane film such as the JPS polyurethane film available from JPS Elastomerics Corp, Northampton, Mass. The thin film membrane covering the microphone is approximately the size and shape of a small thimble, that is, about xc2xd inch diameter by xc2xd inch long, tapering to a closed end. To achieve the desired properties, that is, preventing contamination from environmental agents as well as transmitting sound, the thickness of the membrane can be as great as 0.004 inches thick near the open end, thinning down quickly to no greater than about 0.001 inches for the rest of the membrane. The primary concern relative to environmental contamination is water and water vapor. If the microphone is exposed to water or water vapor, it will, in time become compromised and fail to function. A typical microphone incorporates either a very fine metallic screen or a plate with a series of small holes. Such coverings rely on the surface tension of water, a highly polar molecule, to prevent water molecules from passing through. Often in rainy weather conditions this results in the formation of a film of water across the surface of the protective screen and tends to inhibit the transmission of sound. Such protection is only minimally effective for incidental contact with water droplets, such as would be encountered in a light rain or water sprinkle. However, in many uses the microphone is exposed to heavy rains and even water submersion as well as high humidity from the user""s exhaled breath and/or ambient air. In high humidity, water vapor passes easily through the screen or holes and ultimately condenses back to liquid water on the inside of the microphone element. Frequently, a microphone used in outdoor environments is exposed to other contaminants, such as salt, which may result corrosion. The membrane employed in the present communications headset resolves such problems by completely isolating the microphone element from the ambient atmosphere. The membrane is sealed in a watertight manner at its base, that is at the open end, to the inside of the microphone cover. Thus, in the present invention the membrane-protected microphone can be exposed to liquid water and water vapor as well as other liquids and vapors without deleterious effect. The chemical resistance and compatibility of the membrane material will dictate which chemicals the microphone boom module can be exposed to. The mechanical properties of the membrane as well as its shape and thickness may affect the sound wave transmission of the microphone element. In general, the greater the hardness or stiffness of the membrane material, the more important it becomes that the thickness be minimal. The distance that the membrane is from the face of the microphone is also important. If the distance is too great, the sound waves will not be transmitted to the microphone clearly. Typically, it is preferred that the distance between the face of the microphone and the membrane is between about 0.002 to 0.008 inch. At lesser distances feedback may become a problem. At greater distances sound wave transmission may deteriorate.
In order for the membrane to allow adequate sound transmission to the microphone, it must remain flexible. Occasionally, environmental changes in pressure, such as during shipment in an aircraft, may cause a pressure differential across the membrane, resulting in reduced flexibility of the membrane. To compensate for such changes in pressure, it has been found preferable to pierce the membrane, using for example, a very sharp-pointed pin or needle. The resultant puncture in the membrane will then function as a pressure release valve when a pressure differential occurs and will close when the pressure is nearly equalized. Thus, the puncture will allow for pressure equalization while still maintaining the integrity of the membrane and its ability to prevent the passage of water and water vapor during normal use.
The other thin film membrane incorporated in the present headset, the ear cup membrane, may be made of a similar or same material as the microphone cover membrane but will vary somewhat in properties and shape. This membrane is designed to fit into the ear cup in such a way that it forms a contamination barrier between the internal components of the ear cup and the ambient surroundings. The ear cup membrane has a uni-planar flange area forming the outside perimeter and shaped to match the ear up cushion and be mechanically held between the ear cup cushion and the ear cup plate. preferably, the flange area of the membrane is approximately 0.005 inches thick. The center region of the membrane is concave in shape recessing into the internal pocket portion of the ear cup. The membrane thickness of this center region is preferably no greater than about 0.001 inches thick in order to allow acceptable transmission of sound waves between the headset speaker and the user""s ear.